Making a pasted image opaque

[Wilhelm Sanke]

Postscript:

One problem of my proposed script is that restoring the original opaque 
colors of the image is only possible if the alphadata values are above 0.
If the transparency was set to 0, resetting the values to 255 will 
result in dark or black color values for all alphadata chars with 0.

In the forthcoming version of my Imagedata Toolkit the transparency 
effects have  "1" as the value for the greatest transparency, which 
preserves the original colors when you change the transparency level.

So indeed, the safest way is to follow Scott Rossi's proposal to take a 
snapshot of the rect of the image against a white background.

Regards,

Wilhelm Sanke
<http://www.sanke.org/MetaMedia>